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Laser Doppler Measurements of Turbulent Parameters in Different Multiple‐Propeller Systems
Author(s) -
Baudou C.,
Xuereb C.,
Costes J.,
Bertrand J.
Publication year - 2000
Publication title -
chemical engineering and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.403
H-Index - 81
eISSN - 1521-4125
pISSN - 0930-7516
DOI - 10.1002/(sici)1521-4125(200003)23:3<257::aid-ceat257>3.0.co;2-4
Subject(s) - turbulence , mechanics , autocorrelation , propeller , microscale chemistry , doppler effect , taylor microscale , laser doppler velocimetry , rushton turbine , physics , dissipation , impeller , eddy , acoustics , turbulence kinetic energy , mathematics , thermodynamics , engineering , statistics , medicine , mathematics education , blood flow , astronomy , marine engineering
In this study, laser Doppler anemometry (LDA) measurements in the r‐z plane are obtained in two stirred tanks equipped with two downward pumping propellers in the turbulent and the transient flow domains. A new approach of the hydrodynamics generated by this system consists of determining the one‐dimensional energy spectrum and the autocorrelation coefficient function at different locations in each vessel. In the turbulent flow, the integral scales, the Taylor microscales, and the Kolmogorov microscale have been determined. The dissipation rate is obtained with two methods: from the semi‐empirical expression ϵ = A k 3/2 /D and from the frequency spectrum. Results show the influence of the rheological properties on the flow patterns, the influence of the blade passage frequency on the frequency spectrum, and the apparition of a low frequency characterizing the production of macro‐instabilities. Comparison of the turbulent characteristics with the values reported in the literature shows that our combination of propellers produces larger eddies than a Rushton turbine.